THE title of the present work is in itself a sufficiently clear indication of the contents. In it, the attempt is made to show the connexion between two sciences whose subject-matters are closely interrelated, but which have, for the most part, followed wholly divergent paths. Physiology and psychology cover, between them, the field of vital phenomena; they deal with the facts of life at large, and in particular with the facts of human life. Physiology is concerned with all those phenomena of life that present them selves to us in sense perception as bodily processes, and accordingly form part of that total environment which we name the external world. Psychology, on the other hand, seeks to give account of the interconnexion of processes which are evinced by our own consciousness, or which we infer from such manifestations of the bodily life in other creatures as indicate the presence of a consciousness similar to our own.

This division of vital processes into physical and psychical is useful and even necessary for the solution of scientific problems. We must, however, remember that the life of an organism is really one; complex, it is true, but still unitary. We can, therefore, no more separate the processes of bodily life from conscious processes than we can mark off an outer experience, mediated by sense perceptions, and oppose it, as something wholly separate and apart, to what we call 'inner' experience, the events or our own consciousness. On the contrary: just as one and the same thing, e.g., a tree that I perceive before me, falls as external object within the scope of natural science, and as conscious contents within that of psychology, so there are many phenomena of the physical life that are uniformly connected with conscious processes, while these in turn are always bound up with processes in the living body. It is a matter of every-day experience that we refer certain bodily movements directly to volitions, which we can observe as such only in our consciousness. Conversely, we refer the ideas of external objects that arise in consciousness either to direct affection of the organs of sense, or, in the case of memory images, to physiological excitations within the sensory centres, which we interpret as after-effects of foregone sense impressions.

[p. 2] It follows, then, that physiology and psychology have many points of contact. In general there can of course be no doubt that their problems are distinct. But psychology is called upon to trace out the relations that obtain between conscious processes and certain phenomena of the physical life; and physiology, on its side, cannot afford to neglect the conscious contents in which certain phenomena of this bodily life manifest them selves to us. Indeed, as regards physiology, the interdependence of the two sciences is plainly in evidence. Practically everything that the physiologists tell us, by way of fact or of hypothesis, concerning the processes in the organs of sense and in the brain, is based upon determinate mental symptoms: so that psychology has long been recognised, explicitly or implicitly, as an indispensable auxiliary of physiological investigation. Psychologists, it is true, have been apt to take a different attitude towards physiology. They have tended to regard as superfluous any reference to the physical organism; they have supposed that nothing more is required for a science of mind than the direct apprehension of conscious processes themselves. It is in token of dissent from any such standpoint that the present work is entitled a "physiological psychology." We take issue, upon this matter, with every treatment of psychology that is based on simple self-observation or on philosophical presuppositions. We shall, wherever the occasion seems to demand, employ physiology in the service of psychology. We are thus, as was indicated above, following the example of physiology itself, which has never been in a position to disregard facts that properly belong to psychology, - although it has often been hampered in its use of them by the defects of the empirical or metaphysical psychology which it has found current.

Physiological psychology is, therefore, first of all psychology. It has in view the same principal object upon which all other forms of psychological exposition are directed: the investigation of conscious processes in the modes of connexion peculiar to them. It is not a province of physiology; nor does it attempt, as has been mistakenly asserted, to derive or explain the phenomena of the psychical from those of the physical life. We may read this meaning into the phrase 'physiological psychology,' just as we might interpret the title 'microscopical anatomy' to mean a discussion, with illustrations from anatomy, of what has been accomplished by the microscope; but the words should be no more misleading in the one case than they are in the other. As employed in the present work, the adjective 'physiological' implies simply that our psychology will avail itself to the full of the means that modern physiology puts at its disposal for the analysis of conscious processes. It will do this in two ways.

(I) Psychological inquiries have, up to the most recent times, been undertaken solely in the interest of philosophy ; physiology was enabled, by [p. 3] the character of its problems, to advance more quickly towards the application of exact experimental methods. Since, however, the experimental modification of the processes of life, as practised by physiology, oftentimes effects a concomitant change, direct or indirect, in the processes of consciousness,--which, as we have seen, form part of vital processes at large,--it is clear that physiology is, in the very nature of the case, qualified to assist psychology on the side of method; thus rendering the same help to psychology that it, itself received from physics. In so far as physiological psychology receives assistance from physiology in the elaboration of experimental methods, it may be termed experimental psychology. This name suggests, what should not be forgotten, that psychology, in adopting the experimental methods of physiology, does not by any means take them over as they are, and apply them without change to a new material. The methods of experimental psychology have been transformed--in some instances, actually remodelled--by psychology itself, to meet the specific requirements of psychological investigation. Psychology has adapted physiological as physiology adapted physical methods, to its own ends.

(2) An adequate definition of life, taken in the wider sense, must (as we said just now) cover both the vital processes of the physical organism and the processes of consciousness. Hence, wherever we meet with vital phenomena that present the two aspects, physical and psychical there naturally arises a question as to the relations in which these aspects stand to each other. So we come face to face with a whole series of special problems, which may be occasionally touched upon by physiology or psychology, but which cannot receive their final solution at the hands of either, just by reason of that division of labour to which both sciences alike stand committed. Experimental psychology is no better able to cope with them than is any other form of psychology, seeing that it differs from its rivals dilly in method, and not in aim or purpose. Physiological psychology, on the other hand, is competent to investigate the relations that hold between the processes of the physical and those of the mental life. And in so far as it accepts this second problem, we may name it a psychophysics.[1] If we free this term from any sort of metaphysical implication [p. 4] as to the relation of mind and body, and understand by it nothing more than an investigation of the relations that may be shown empirically to obtain between the psychical and the physical aspects of vital processes, it is clear at once that psychophysics becomes for us not, what it is some times taken to be, a science intermediate between physiology and psychology, but rather a science that is auxiliary to both. It must, however, render service more especially to psychology, since the relations existing between determinate conditions of the physical organization, on the one hand, and the processes of consciousness, on the other, are primarily of interest to the psychologist. In its final purpose, therefore, this psychophysical problem that we have assigned to physiological psychology proves to be itself psychological. In execution, it will he predominantly physiological since psychophysics is concerned to follow up the anatomical and physiological investigation of the bodily substrates of conscious processes, and to subject its results to critical examination with a view to their bearing upon our psychical life.

There are thus two problems which are suggested by the title "physiological psychology": the problem of method, which involves the application of experiment, and the problem of a psychophysical supplement, which involves a knowledge of the bodily substrates of the mental life. For psychology itself, the former is the more essential; the second is of importance mainly for the philosophical question of the unitariness of vital processes at large. As an experimental science, physiological psychology seeks to accomplish a reform in psychological investigation comparable with the revolution brought about in the natural sciences by the introduction of the experimental method. From one point of view, indeed, the change wrought is still more radical: for while in natural science it is possible under favourable conditions, to male an accurate observation without recourse to experiment, there is no such possibility in psychology. It is only with grave reservations that what is called 'pure self-observation' can properly be termed observation at all and under no circumstances can it lay claim to accuracy. On the other hand, it is of the essence of experiment that we can vary the conditions of an occurrence at will and, if we are aiming at exact results; in a quantitatively determinable way Hence, even in the domain of natural science the aid of the experimental method becomes indispensable whenever the problem set is the analysis of transient and impermanent phenomena, and not merely the observation of persistent and relatively constant objects. But conscious contents are at the opposite pole from permanent objects; they are processes, fleeting occurrences, in continual flux and change. In their case, therefore, the experimental method is of cardinal importance; it and it alone males a scientific introspection possible. For all accurate observational implies that the object [p. 5] of observation (in this case the psychical process) can be held fast by the attention, and any changes that it undergoes attentively followed. And this fixation by the attention implies, in its turn, that the observed object is independent of the observer. Now it is obvious that the required independence does not obtain in any attempt at a direct self-observation, undertaken without the help of experiment. The endeavour to observe oneself must inevitably introduce changes into the course of mental events,--changes which could not have occured without it, and whose usual consequence is that the very process which was to have been observed disappears from consciousness. The psychological experiment proceeds very differently. In the first place, it creates external conditions that look towards the introduction of a determinate mental process at a given moment. In the second place, it makes the observer so far master of the general situation, that the state of consciousness accompanying this process remain approximately unchanged. The great importance of the experimental method, therefore, lies not simply in the fact that, here as in the physical realm, it enables us arbitrarily to vary the conditions of our observations, but also and essentially in the further fact that it makes observation itself possible for us. The results of this observation may then be fruitfully employed in the examination of other mental phenomena, whose nature prevents their own direct experimental modification.

We may add that, fortunately for the science, there are other sources of objective psychological knowledge, which become accessible at the very point which the experimental method fails us. These are certain products of the common mental life, in which we may trace the operation of determinate psychical motives: chief among them are language, myth and custom. In part determined by historical conditions, they are also, in part dependent upon universal psychological laws; and the phenomena that are referable to these laws form the subject-matter of a special psychological discipline, ethnic psychology. The results of ethnic psychology constitute, at the same time, our chief source of information regarding the general psychology of the complex mental processes. In this way, experimental psychology and ethnic psychology form the two principal departments of scientific psychology at large. They are supplemented by child and animal psychology, which in conjunction with ethnic psychology attempt to resolve the problems of psychogenesis. Workers in both these fields may, of course, avail themselves within certain limits of the advantages of the experimental method. But the results of experiment are here matters of objective observation only, and the experimental method accordingly loses the peculiar significance which it possesses as an instrument of introspection. Finally, child psychology and experimental psychology in the narrower sense may be bracketed together as individual [p. 6] psychology while animal psychology and ethnic psychology form the two halves of a generic or comparative psychology. These distinctions within psychology are, however, by no means to be put on a level with the analogous divisions of the province of physiology. Child psychology and animal psychology are of relatively slight importance, as compared with the sciences which deal with the corresponding physiological problems of ontogeny and phylogeny. On the other hand, ethnic psychology must always come to the assistance of individual psychology, when the developmental forms of the complex mental processes are in question.

Kant once declared that psychology was incapable of ever raising itself to the rank of an exact natural science.[2] The reasons that he gives for this opinion have often been repeated in later times.[3] In the first place, Kant says, psychology cannot become an exact science because mathematics is inapplicable to the phenomenon of the internal sense; the pure internal perception, in which mental phenomena must be constructed,--time,--has but one dimension. In the second place, however, it cannot even become an experimental science, because in it the manifold of internal observation cannot be arbitrarily varied,--still less, another thinking subject be submitted to one's experiments, conformably to the end in view; moreover, the very fact of observation means alteration of the observed object. The first of these objections is erroneous; the second is, at the least, one-sided. It is not true that the course of inner events evinces only one dimension, time. If this were the case, its mathematical representation would, certainly be impossible; for such representation always requires at least two variables, which can be subsumed under the concept of magnitude. But, as a matter of fact, our sensations and feelings are intensive magnitudes, which form temporal series. The course of mental events has, therefore, at any rate two dimensions; and with this fact is given the general possibility of its presentation in mathematical form. Otherwise, indeed Herbart could hardly have lighted upon the idea of applying mathematics to psychology. And his attempt has the indisputable merit of proving once and for all the possibility of an application of mathematical methods in the sphere of mind.[4]

If Herbart, nevertheless, failed to accomplish the task which he set himself, the reason of his failure is very simple; it lay in the overweening confidence with which he regarded the method of pure self-observation and the hypotheses whereby he filled out the gaps that this observation leaves. It is Fechner's service to have found and followed the true way; to have shown us how a 'mathematical psychology' may, within certain limits, be realised in practice. Fechner's method consists in the experimental modification of consciousness by sensory stimuli; it leads, under favourable circumstances, to the establishment
of certain quantitative relations between the physical and the psychical.[5]At [p. 7] the present day, experimental psychology has ceased to regard this formulation of mental measurements as its exclusive or even as its principal problem. Its aim is now more general; it attempts, by arbitrary modification of consciousness, to arrive at a causal analysis of mental processes. Fechner's determinations are also affected, to some extent, by his conception of Psychophysics as a specific science of the 'interactions of mind and body.' But, in saying this, we do not lessen the magnitude of his achievement. He was the first to show how Herbart's idea of an 'exact psychology' might be turned to practical account.

The arguments that Kant adduces in support of his second objection, that the inner experience is inaccessible to experimental investigation, are all derived from purely internal sources, from the subjective flow of processes; and there, of course, we cannot challenge its validity. Our psychical experiences are, primarily, indeterminate magnitudes; they are incapable of exact treatment until they have been referred to determinate units of measurement, which in turn may be brought into constant causal relations with other given magnitudes. But we have, in the experimental modification of consciousness by external stimuli, a means to this very end,--to the discovery of the units of measurement and the relations required. Modification from without enables us to subject our mental processes to arbitrarily determined conditions, over which we have complete control and which we may keep constant or vary as we will. Hence the objection urged against experimental psychology, that it seeks to do away with introspection, which is the sine qua non of any psychology, is based upon a misunderstanding. The only form of introspection which experimental psychology seeks to banish from the science is that professing self-observation which thinks it can arrive directly, without further assistance, at an exact characterisation of mental facts, and which is therefore inevitably exposed to the grossest self-deception. The aim of the experimental procedure is to substitute for this subjective method, whose sole resource is an inaccurate inner perception, a true and reliable introspection, and to this end it brings consciousness under accurately adjustable objective conditions. For the rest, here as elsewhere, we must estimate the value of the method, in the last resort, by its results. It is certain that the subjective method has no success to boast of; for there is hardly a single question of fact upon which its representatives do not hold radically divergent opinions. Whether and how far the experimental method is in better cast, the reader will be able to decide for himself at the conclusion of this work. He must, however, in all justice remember that the application of experiment to mental problems is still only a few decades old.[6]

The omission, in the above list of the various psychological disciplines, of any mention of what is called rational psychology is not accidental. The term was introduced into mental science by C. Wolff (1679-1754), to denote a knowledge of the mental life gained, in independence of experience, simply and solely [p. 8] from metaphysical concepts. The result has proved, that any such metaphysical treatment of psychology must, if it is to maintain its existence, be constantly making surreptitious incursions into the realm of experience. Wolff himself found it necessary to work out an empirical psychology, alongside of the rational: though it must be confessed that, in fact, the rational contains about as much experience as the empirical and the empirical about as much metaphysics as the rational. The whole distinction rests upon a complete misapprehension of the scientific position, not only of psychology, but also of philosophy. Psychology is, in reality, just as much an experiential science as is physics or chemistry. But it can never be the business of philosophy to usurp the place of any special science; philosophy has its beginnings, in every case, in the established results of the special sciences. Hence the works upon rational psychology stand in approximately the same relation to the actual progress of psychological science as does the nature-philosophy of Schelling or Hegel to the development of modern natural science.[7]

There are certain psychological works, still current at the present time, which bear the word 'empirical' upon their title-pages, but make it a matter of principle to confine themselves to what they term a 'pure' introspection. They are, for the most part, curious mixtures of rational and empirical psychology. Sometimes the rational part is restricted to a few pages of metaphysical discussion of the nature of mind; sometimes- as in the great majority of books of the kind emanating from the Herbartian School --certain hypotheses of metaphysical origin are put forward as results of self-observation. It has been well said that if a prize were offered to the discovery by this whole introspective school of one single undisputed fact, it would be offered in vain.[8] Nevertheless, the assurance of the Herbartians is incredible. Their compendia appear, one after another; and the memory of the students who use them is burdened with a mixed medley of purely imaginary processes. On the other side, the supreme advantage of the experimental method lies in the fact that it and it alone renders a reliable introspection possible, and that it therefore increases our ability to deal introspectively with processes not directly accessible to modification from without. This general significance of the experimental method is being more and more widely recognised in current psychological investigation; and the definition of experimental psychology has been correspondingly extended beyond its original limits. We now understand by 'experimental psychology' not simply those portions of psychology which are directly accessible to experimentation, but the whole of individual psychology. For all such psychology employs the experimental method: directly, where its direct use is possible; but in all other cases indirectly, by availing itself of the general results which the direct employment of the method has yielded, and of the refinement of psychological observation which this employment induces.

Experimental psychology itself has, it is true, now and again suffered relapse into a metaphysical treatment of its problems. We recognise the symptoms whenever we find 'physiological psychology' defined, from the outset, in such a way as to give it a determinate metaphysical implication. The task now assigned to the science is that of the interpretation of conscious phenomena by [p. 9] their reference to physiological conditions. Usually, the infection spreads still farther, and the same view is taken of the problem of psychology at large. As regards sensations, the elements out of which they are compounded, conscious processes (we are told) have their specific character, their peculiar constitution; but it is impossible by psychological means to discover uniformities of connexion among these elements. Hence the only road to a scientific description or explanation of complex mental experiences lies through the knowledge of the physiological connexions obtaining among the physiological processes with which the psychical elements are correlated.[9] On this conception, there is no such thing as psychical, but only psychical causation, and every causal explanation of mental occurrence must consequently be couched in physiological terms. It is accordingly termed the theory of 'psychophysical materialism.' The theory as such is by no means a new thing in the history of philosophy. All through the eighteenth century it was struggling for mastery with the rival theory of mechanical materialism, which explained the psychical elements themselves as confused apprehensions of molecular motions. But it presents a novel feature in its endeavour to press physiological psychology into the service of the metaphysical hypothesis and thus apparently to remove this hypothesis from the metaphysical sphere,--so that psychological materialism becomes for its representatives compatible even with a philosophical idealism of the order of Kant or Fichte. Since psychology, from this point of view, forms a supplement to physiology, and therefore takes its place among the natural sciences, it need, as a matter of fact, pay no further regard either to philosophy or to the mental sciences. That the mental life itself is the problem of psychology,--this is mere dogma, handed down to us by past ages.[10]Yet after all, the assertion that there is no such thing as psychical causation, and that all psychical connexions must be referred back to physical, is at the present day this: it is an assumption which, on its negative side, comes into conflict with a large number of actually demonstrable psychical connexions, and, on the positive, raises a comparatively very limited group of experiences to the rank of an universal principle. It is, we must suppose, a realisation of the inadequacy of the arguments offered in support of these two fundamental implications that has led certain psychologists, who would otherwise take the same theoretical position, to divide the problem of psychology, and to recognise the interconnexions of mental processes as a legitimate object of inquiry, alongside of the investigation of their dependence upon determinate physiological process within the brain. In the psychological portion of their works, these writers usually adopt the theory of the 'association of ideas,' elaborated in the English psychology of the eighteenth century.[11] They adopt it for the good and sufficient reason that the doctrine of association, from David Hartley (1705-1757) [p. 10] down to Herbert Spencer (1820-1904), has itself for the most part attempted merely a physiological interpretation of the associative processes.

The materialistic point of view in psychology can claim, at best, only the value of an heuristic hypothesis. Its justification must, therefore, be sought first of all in its results. But it is apparent that the diversion of the work of psychology from its proper object, the related manifold of conscious processes, is precisely calculated to make the experimental method comparatively barren, so far as concerns psychology itself. And, as a matter of fact, the books upon physiological psychology that are written from the standpoint of materialism confine themselves almost entirely, when they are not borrowing from the physiology of brain and sense organs, to the beaten track of the traditional doctrine of association. Ideas are treated, after as before, as if they were immutable objects, that come and go, form connexions of sequence with one another, obey in these connexions the well-known laws of habit and practice, and finally, when arranged in certain groups, yield the not very startling result that they can be brought under the same logical categories that have proved generally serviceable for the classification of all sorts of concepts.[12]

Now physiology and psychology, as we said just now, are auxiliary disciplines, and neither can advance without assistance from the other. Physiology, in its analysis of the physiological functions of the sense organs, must use the results of subjective observation of sensations; and psychology, in its turn, needs to know the physiological aspects of sensory function, in order rightly to appreciate the psychological. Such instances might easily be multiplied. Moreover, in view of the gaps in our knowledge, physiological and psychological alike, it is inevitable that the one science will be called upon, time and again, to do duty for the other. Thus, all our current theories of the physical processes of light excitation are inferences from the psychological course and character of visual sensations; and we might very well attempt, conversely, to explain the conditions of practice and habituation, in the mental sphere, from the properties of nervous substance, as shown in the changes of excitability due to the continued effect of previous excitations. But one cannot assert, without wilfully closing one's eyes to the actual state of affairs or taking theories for facts, that the gaps in our knowledge which demand this sort of extraneous filling are to be found only on the one side, the side of psychology. In which of the two sciences our knowledge of processes and of the interconnexion of processes is more or less perfect or imperfect is a question that, we may safely say, hardly admits of an answer. But however this may be, the assertion that the mental life lacks all causal connexion, and that the real and primary object of psychology is therefore not the mental life itself but the physical substrate of that life,--this assertion stands self-condemned. The effects of such teaching upon psychology cannot but be detrimental. In the first place, it conceals the proper object of psychological investigation behind facts and hypotheses that are borrowed from physiology. Secondly and more especially, it recommends the employment of the experimental methods without the least regard to the psychological point of view, so that for psychology as such their results are generally valueless. Hence the gravest danger that besets the path of our science today comes not from the speculative and empirical dogmas of the older schools, but [p. 11] rather from this materialistic pseudo-science. Antipsychological tendencies can hardly find clearer expression than in the statement that the psychological interpretation of the mental life has no relation whatever to the mental life itself, as manifested in history and in society.

Besides this application of the term 'experimental psychology' in the interests of psychological materialism, we find it used in still another sense, which is widely different from that of our own definition. It has become customary, more especially in France, to employ the name principally, if not exclusively, for experiments upon hypnotism and suggestion. At its best, however, this
usage narrows the definition of 'experimental psychology' in a wholly inacceptable way. If we are to give the title of 'psychological experiment' to each and every operation upon consciousness that brings about a change of conscious contents, then, naturally, hypnotisation and the suggestion of ideas must be accounted experiments. The inducing of a morphine narcosis, and any purposed interference with the course of a dream consciousness, would fall under the same category. But if the principal value of the psychological experiment lies in the fact that it makes an exact introspection possible, very few of these modifications of consciousness can be termed true psychological experiments. This does not mean of course, that experiments with suggestion may not, under favourable circumstances,--in the hands of an experimenter who is guided by correct psychological principles, and who has at his command reliable and introspectively trained observers,--yield results of high importance to psychology: so much, indeed, is proved by Vogt's observations on the analysis of the feelings in the hypnotic state.[13] But in such cases the conditions necessary to the performance of accurate experiments are, it is plain, peculiarly difficult of fulfilment; and the great majority of what are called 'hypnotic experiments' either possess, accordingly, no scientific value at all or lead to the observation of interesting but isolated facts, whose place in the psychological system is still uncertain.[14]

§2. Survey of the Subject

Physiological psychology is primarily psychology and therefore has for its subject the manifold of conscious processes, whether as directly experienced by ourselves, or as inferred on the analogy of our own experiences from objective observation. Hence the order in which it takes up particular problems will be determined primarily by psychological considerations; the phenomena of consciousness fall into distinct groups, according to the points of view from which they are successively regarded. At the same time, any detailed treatment of the relation between the psychical and physical aspects of vital processes presupposes a digression into anatomy and physiology such as would naturally be out of place in a purely psychological exposition. While, then, the following Chapters of this work are arranged in general upon a systematic plan, the author has not always observed the rule that the reader should be adequately prepared, at each stage [p. 12] of the discussion, by table contents of preceding Chapters. Its disregard has enabled him to avoid repetition; and he has acted with the less scruple, in view of the general understanding of psychology which the rending of a book like the present implies. Thus a critical review of the results of brain anatomy and brain physiology, with reference to their value for psychology, presupposes much and various psychological knowledge. Nevertheless, it is necessary, for other reasons, that the anatomical and physiological considerations should precede the properly psychological portion of the work. And similar conditions recur, now and again, even in Chapters that are pre-eminently psychological.[l5]

Combining in this way the demands of theory and the precepts of practical method, we shall in what follows (1) devote a first Part to the bodily substrate of the mental life. A wealth of new knowledge is here placed at our disposal by the anatomy and physiology of the central nervous system, reinforced at various points by pathology and general biology. This mass of material calls imperatively for examination from the psychological side: more especially since it has become customary for the sciences concerned in its acquisition to offer all varieties of psychological interpretation of their facts. Nay, so far have things gone, that we actually find proposals made for a complete reconstruction of psychology itself, upon an anatomical and physiological basis! But, if we are seriously to examine these conjectures and hypotheses, we must, naturally, acquaint ourselves with the present status of the sciences in question. Even here, however, our presentation of the facts will depart in some measure from the beaten path. Our aim is psychological: so that we may restrict ourselves, on the one hand, to matters of general importance, while on the other we must lay special emphasis upon whatever is significant for psychology. Thus it cannot be our task to follow brain anatomy into all the details which it has brought to light concerning the connexions of fibres within the brain,--into all those minute points whose interpretation is still altogether uncertain, and whose truth is often and again called in question. It will only be necessary for us to obtain a general view of he structure of the central organs and of such principal connexions of these with one another and with the peripheral organs as have been made out with sufficient certainty. We may then in the light of reasonably secure principles of nerve physiology and of our psychological knowledge, proceed to discuss the probable relations of physiological structure and function to the processes of consciousness.

(2) We shall then, in a second Part, begin our work upon the problem [p. 13] of psychology proper, with the doctrine of the elements of the mental life. Psychological analysis leaves us with two such elements, of specifically different character: with sensations, which as the ultimate and irreducible elements of ideas we may term the objective elements of the mental life, and with feelings, which accompany these objective elements as their subjective complements, and are referred not to external things but to the state of consciousness itself. In this sense, therefore, we call blue, yellow, warm, cold, etc., sensations; pleasantness, unpleasantness, excitement, depression, etc., feelings. It is important that the terms he kept sharply distinct, in these assigned meanings, and not used indiscriminately, as they often are in the language of everyday life, and even in certain psychologies. It is also important that they be reserved strictly for the psychical elements, and not applied at random both to simple and to complex contents,--a confusion that is regrettably current in physiology. Thus in what follows we shall not speak of a manifold of several tones or of a coloured extent as a 'sensation', but as an 'idea'; and when we come to deal with the formations resulting from a combination of feelings we shall term them expressly 'complex feelings' or (if the special words that language offers us are in place) 'emotions,' 'volitions,' etc. This terminological distinction cannot of course, tell us of itself anything whatsoever regarding the mode of origin of such complex formations from the psychical elements. It does, however, satisfy the imperative requirement that the results of psychological analysis of complex conscious contents be rendered permanent, when that analysis is completed, by fitting designations. As for these results themselves, it need hardly be said that the mental elements are never given directly as contents of consciousness in the uncompounded state. We may learn here from physiology, which has long recognised the necessity of abstracting, in its investigations of these products of analysis, from the connexions in which they occur. Sensations like red, yellow, warm, cold, etc., are considered by physiologists in this their abstract character, i.e., without regard to the connexions in which, in the concrete case, they invariably present themselves. To employ the single term 'sensation' as well for these ultimate and irreducible elements of our ideas as for the surfaces and objects that we perceive about us is a confusion of thought which works sufficient harm in physiology, and which the psychologist must once and for all put behind him.

But there is another and a still worse terminological obscurity, common both to physiology and to psychology, which has its source in the confusion of conscious processes themselves with the outcome of a inner reflection upon their objective conditions. It is all too common to find sensations so named only when they are directly aroused by external sensory stimuli; while the sensations dependent upon any sort of internal condition are termed ideas, [p. 14] and the word idea itself is at the same time restricted to the contents known as memory images. This confusion is psychologically inexcusable. There is absolutely no reason why a sensation -- blue, green, yellow, or what not -- should be one thing when it is accompanied simply by an excitation in the 'visual centre' of the cortex, and another and quite a different thing where this excitation is itself set up by the operation of some external stimulus. As conscious contents, blue is and remains blue, and the idea of an object is always a thing ideated in the outside world, whether the external stimulus or the thing outside of us be really present or not. It is true that the memory image is, oftentimes, weaker and more transient then the image of direct perception. But this difference is by no means constant; we may sense in dreams, or in the state of hallucination, as intensively as we sense under the operation of actual sensory stimuli.[16] Such distinctions are, therefore, survivals from the older psychology of reflection, in which the various contents of consciousness acquired significance only as the reflective thought of the philosopher read a meaning into them. It was an accepted tenet of this psychology that ideas enjoy an immaterial existence in the mind, while sensation was regarded as something that makes its way into mind from the outside. Now all this may be right or wrong; but, whether right or wrong, it evidently has no bearing whatever upon the conscious process as such.

The attitude of physiological psychology to sensations and feelings, considered as psychical elements, is, naturally, the attitude of psychology at large. At the same time, physiological psychology has to face a number of problems which do not arise for general psychology: problems that originate in the peculiar interest which attaches to the relations sustained by these ultimate elements of the mental life to the physical processes in the nervous system and its appended organs. Physiology tells us, with ever increasing conviction, that these relations, especially in the case of sensations, are absolutely uniform; and with an improved understanding of bodily expression, of affective symptomatology, we are gradually coming to see that the feelings too have their laws of correlation, no less uniform, if of an entirely different nature. But this growth of knowledge lays all the heavier charge upon psychology to determine the significance of the various psychophysical relations. A pure psychology could afford, if needs must, to pass them by, and might confine itself to a description of the elements and of their direct interrelations. A physiological psychology, on the other hand, is bound to regard this psychophysical aspect of the problems of mind as one of its most important objects of investigation.

(3) The course of our inquiry proceeds naturally from the mental ele-[p. 15] ments to the complex psychical processes that take shape in consciousness from the connexion of the elements. These mental formations must be treated in order; and our third Part will be occupied with that type of complex process to which all others are referred as concomitant processes: with the items that arise from the connexion of sensations. Since physiological psychology stands committed to the experimental method, it will here pay most regard to the sense ideas aroused by external stimuli, these being most easily brought under experimental control. We may accordingly designate the contents of this section a study of the composition of sense ideas. Our conclusions will however, apply equally well to ideas that are not aroused by external sensory stimuli; the two classes of ideas agree in all essential characters, and are no more to be separated than are the corresponding sensations.

The task of physiological psychology remains the same in the analysis of ideas that it was in the investigation of sensations: to act as mediator between the neighbouring sciences of physiology and psychology. At the same time, the end in view all through the doctrine of ideas is pre-eminently psychological; the specifically psychophysical problems, that are of such cardinal importance for the theory of sensation, now retire modestly into the background. Physiological psychology still takes account of the physical aspect of the sensory functions involved, but it hardly does more in this regard than it is bound to do in any psychological inquiry in which it avails itself of the experimental means placed at its disposal.

(4) The doctrine of sense ideas is followed by a fourth Part, dealing with the analysis of mental processes that, as complex products of the interconnexion of simple feelings, stand in a relation to the affective elements analogous to that sustained by ideas to the sensations of which they are compounded. It must not, of course, be understood that the two sets of formations can, in reality, be kept altogether separate and distinct. Sensations and feelings are, always and everywhere, complementary constituents of our mental experiences. Hence the conscious contents that are compounded of feelings can never occur except together with ideational contents, and in many cases the affective elements are as powerful to influence sensations and ideas as these are to influence the feelings. This whole group of subjective experiences; in which feelings are the determining factors, maybe brought under the title of Gemuthsbewegungen und Willenshandlungun. Of these, Gemuthsbewegungen is the wider term, since it covers volitional as well as affective processes. Nevertheless, in view of the peculiar importance of the phenomena of will, and of the relation which external voluntary actions bear to other organic movements,--a relation whose psychophysical implications constitute it a special problem of physiological psychology,--we retain the two words side by side in the title of our section, and limit the meaning [p. 16] of Gemuthsbewegungen on the one hand to the emotions, and on the other to a class of affective processes that are frequently bound up with or pass into emotions, the intellectual feelings.[17]

(5) Having thus investigated sense ideas, emotions and voluntary actions, the complex processes of the mental life, we pass in a fifth Part to the doctrine of consciousness and of the interconnexion of mental processes. The results of the two preceding sections now form the basis of an analysis of consciousness and of the connexions of conscious contents. For all these conscious connexions contain, as their proximate constituents, ideas and emotion and consciousness itself is nothing else than a general name for the total sum of processes and their connexions. So far as our analysis of these connexions is experimental we shall he chiefly concerned with the arbitrary modification of sense ideas and of their course in consciousness. When, on the other hand, we come to consider the interconnexions of emotions and voluntary actions, our principal dependence will be upon the results of analysis of the processes of consciousness at large.

In these five Parts, then, we confine ourselves to a purely empirical examination of the facts. (6) A sixth and final Part will treat of the origin and principles of mental development. Here we shall endeavour to set forth, in brief, the general conclusions that may be drawn from these facts for a comprehensive theory of the mental life and of its relation to our physical existence. So far, we have set conscious processes and the processes of the bodily life over against each other, without attempting any exact definition of either. Now at last, when our survey of their interrelations is completed, we shall be able to ascribe a definitive meaning to the terms physical and psychical. And this will help us towards a solution of the well worn problem of 'the interaction of mind and body,' a solution that shall do justice to the present status of our physiological and psychological knowledge, and shall also meet the requirements of a philosophical criticism of knowledge itself. Physiological psychology thus ends with those questions with which the philosophical psychology of an older day was wont to begin,--the questions of the nature of the mind, and of the relation of consciousness to an external world; and with a characterisation of the general attitude which psychology is to take up, when it seeks to trace the laws of the mental life as manifested in history and in society.

The human mind is so constituted, that it cannot gather experiences [p. 17] without at the same time supplying an admixture of its own speculation. The first result of this naive reflection is the system of concepts which language embodies. Hence, in all departments of human experience, there are certain concepts that science finds ready made, before it proceeds upon its own proper business,--results of that primitive reflection which have left its permanent record in the concept-system of language. 'Heat' and 'light,' e.g., are concepts from the world of external experience, which had their immediate origin in sense-perception. Modern physics subsumes them both under the general concept of motion. But it would not be able to do this, if the physicist had not been willing provisionally to accept the concepts of the common consciousness, and to begin his inquiries with their investigation. 'Mind,' 'intellect,' 'reason,' 'understanding,' etc., are concepts of just the same kind, concepts that existed before the advent of any scientific psychology. The fact that the naive consciousness always and everywhere points to internal experience as a special source of knowledge, may, therefore, be accepted for the moment as sufficient testimony to the rights of psychology as science. And this acceptance implies the adoption of the concept of 'mind,' to cover the whole field of internal experience. ' Mind,' will accordingly be the subject, to which we attribute all the separate facts of internal observation as predicates. The subject itself is determined wholly and exclusively by its predicates; and the reference of these to a common substrate must be taken as nothing more than an expression of their reciprocal connexion. In saying this, we are declining once and for all to read into the concept of 'mind' a meaning that the naive linguistic consciousness always attaches to it. Mind, in popular thought, is not simply a subject in the logical sense, but a substance, a real being; and the various 'activities of mind' as they are termed, are its modes of expression or action. But there is here involved a metaphysical presupposition, which psychology may possibly be led to honour at the conclusion of her work, but which she cannot on any account accept, untested, before she has entered upon it. Moreover, it is not true of this assumption as it was of the discrimination of internal experience at large, that it is necessary for the starting of the investigation. The words coined by language to symbolise certain groups of experiences still bear upon them marks which show that, in their primitive meanings, their stood not merely [p. 18] for separate modes of existence, for 'substances,' in general but actually for personal beings. This personification of substances has left its most indelible trace in the concept of genus. Now the word-symbols of conceptual ideas have passed so long from hand to hand in the service of the understanding, that they have gradually lost all such fanciful reference. There are many cases in which we have seen the end, not only of the personification of substances, but even of the substantialising of concepts. But we are not called upon, on that account, to dispense with the use whether of the concepts themselves or of the words that designate them. We speak of virtue, honour, reason; but our thought does not translate any one of these concepts into a substance. They have ceased to be metaphysical substances, and have become logical subjects. In the same way, then, we shall consider mind, for the time being, simply as the logical subject of internal experience. Such a view follows directly from the mode of concept-formation employed by language, except that it is freed of all those accretions of crude metaphysics which invariably attach to concepts in their making by the naive consciousness.

We must take up a precisely similar attitude to other ready-made concepts that denote special departments or special relations of the internal experience. Thus our language makes a distinction between 'mind' and 'spirit.' The two concepts carry the same meaning, hut carry it in different contexts: their correlates in the domain of external experience are 'body' and 'matter.' The name 'matter' is applied to any object of external experience as it presents itself directly to our senses, without reference to an inner existence of its own. 'Body' is matter thought of with reference to such an inner existence. 'Spirit,' in the same way, denotes the internal existence as considered out of all connexion With an external existence; whereas 'mind,' especially where it is explicitly opposed to spirit, presupposes this connexion with a corporeal existence, given in external experience.[19]

While the terms 'mind' and 'spirit' cover the whole field of internal experience, the various 'mental faculties,' as they are called, designate the special provinces of mind as distinguished by a direct introspection. Language brings against us an array of concepts like 'sensibility,' 'feeling,' 'reason,' 'understanding,'--a classification of the processes given in internal perception against which, bound down as we are to the use of these words, we are practically powerless. What we call do, however, and what science is obliged to do, is to reach an exact definition of the concepts; and to arrange them upon a systematic plan. It is probable that the mental faculties stood originally not merely for different parts of the field of internal [p. 19] experience, but for as many different beings; though the relation of these to the total being, the mind or spirit, was not conceived of in any very definite way. But the hypostatization of these concepts lies so far back in the remote past, and the mythological interpretation of nature is so alien to our modes of thought, that there is no need here to warn the reader against a too great credulity in the matter of metaphysical substances. Nevertheless, there is one legacy which has come down to modern science from the mythopoeic age. All the concepts that we mentioned just now have retained a trace of the mythological concept of force; they are not regarded simply as--what they really are--class-designations of certain departments of the inner experience, but are oftentimes taken to be forces, by whose means the various phenomena are produced. Understanding is looked upon as the force that enables us to perceive truth; memory as the force which stores up ideas for future use; and so on. On the other hand, the effects of these different 'forces' manifest themselves so irregularly that they hardly seem to be forces in the proper sense of the word; and so the phrase 'mental faculties' came in to remove all objections. A faculty, as its derivation indicates, is not a force that must operate, necessarily and immutably, but only a force that may operate. The influence of the mythological concept of force is here as plain as it could well be; for the prototype of the operation of force as faculty is, obviously, to be found in human action. The original significance of faculty is that of a being which acts. Here, therefore, in the first formation of psychological concepts, we have the germ of that confusion of classification with explanation which is one of the besetting sins of empirical psychology. The general statement that the mental faculties are class concepts, belonging to descriptive psychology, relieves us of the necessity of discussing them and their significance at the present stage of our inquiry. As a matter of fact, one can quite well conceive of a natural science of the internal experience in which sensibility, memory, reason and understanding should be conspicuous by their absence. For the only things that we are directly cognisant of in internal perception are individual ideas, feelings, impulses, etc.; and the subsumption of these individual facts under certain general concepts contributes absolutely nothing toward their explanation.

At the present day, the uselessness of the faculty-concepts is almost universally conceded. Again, however, there is one point in which they still exercise a widespread influence. Not the general class-concepts, but the individual facts that, in the old order of things, were subsumed under them, are now regarded in many quarters as independent phenomena, existing in isolation. On this view there is, to be sure, no special faculty of ideation or feeling or volition; put the individual idea, the individual affective process, and the individual voluntary act are looked upon as inde-[p. 20] pendent processes, connecting with one another and separating from one another as circumstances determine. Now introspection declares that all these professedly independent processes through and through interconnected and interdependent. It is evident, therefore, that their separation involves just the same translation of the products of abstraction into real things as we have charged to the account of the old doctrine of faculties, - only that in this case the abstractions come a little nearer to the concrete phenomena. An isolated idea, an idea that is separable from the processes of feeling and volition, no more exists than does all isolated mental force of 'understanding.' Necessary as these distinctions are, then, we must still never forget that they are based upon abstractions--that they do not carry with them any real separation of objects. Objectively, we can regard the individual mental processes only as inseparable elements of interconnected wholes.

The argument of the text may be supplemented here by some further critical remarks upon the two parallel concepts of 'mind' and 'spirit,' and upon the doctrine of mental faculties.

The English language distinguishes spirit from mind; is a second substance-concept, with the differentia that it is not, as mind is, necessarily bound up, by the mediation of the senses, with a corporeal existence, but either stands in a merely external connexion with body or is entirely free of bodily relations The concept of spirit is accordingly used in a two-fold meaning. On the one hand, it stands for the substrate of all inner experiences which are supposed to be independent of the activity of the senses; on the other, it denotes a being which has no part or lot at all in corporeal existence. It is, of course, only in the former of these two meanings that the concept of spirit comes into psychology. We can, however, see at once that the first signification must logically pass over into the second. If the connexion of spirit with body is merely external and as it were accidental there is no reason why spirit should not occur in the form of pure undivided substance.

Philosophical reflection could not leave the relation of mind and spirit in the obscurity which had satisfied the needs of the naive consciousness. Are mind and spirit different beings? Is mind a part of spirit, or spirit a part of mind? The earliest philosophical speculation shows clearly enough into what perplexity these questions plunged its authors. On the one hand, they are forced by the interconnexion of the inner experience to postulate a single substance as its substrate; on the other, they can see no way to escape a separation of the more abstract spiritual activities from the bodily entanglements of sense-perception. Alongside of the universal dualism of matter and spirit there remains the more restricted antithesis of spirit and mind. And ancient philosophy never succeeded in wholly overcoming this antithesis,--whether, with Plato, it tries to get rid of the substantiality of mind by regarding mind as a mixture of matter and spirit,[20] or whether, with Aristotle, it transfers to spirit the notion that it has abstracted from mind and so substitutes a coincident [p. 21] form of definition for unity of substance.[21] Modern spiritualistic philosophy has, in general, followed the path laid down by PLATO, though it affirms more decidedly than PLATO did the unity of substance in mind and spirit. The result is that all real discrimination of the two concepts disappears from the scientific vocabulary. If a difference is made, it is made in one of to ways, Either spirit is taken as the general concept, within which the individual mind is contained;[22] or spirit is confused with the mental faculties, of which we shall speak presently, and retained as a general designation for the 'higher' mental faculties or, specifically, for intelligence or the faculty of knowledge. The second usage is often accompanied, in the later works, by the inclusion of feeling and desire in the common concept of 'disposition'; so that the mind as a whole divides into intellect and disposition,[23] without any implication of a separation into distinct substances. Sometimes, again, a mere difference of degree is made between the two terms mind and spirit, and spirit ascribed to man, while mind alone is assigned to the animals. Thus the distinction becomes less and less definite, while at the same time the concept of spirit loses its substantial character. So that, if we are to give the worth a meaning that shall not anticipate the results of later investigation, we can do no more than say that spirit, like mind, is the subject of the inner experience, but that in it abstraction is made from the relations of this subject to a corporeal being. Mind is the subject of the inner experience as conditioned by its connexion with an external existence; spirit is the same subject without reference to such connexion. We shall accordingly, speak of spirit and of spiritual phenomena only when we can afford to neglect those moments of the inner experience which render it dependent upon our sensuous existence, i.e., upon that side of our existence which is accessible to external experience. This definition leaves entirely open the question whether spirit really is independent of sensibility. We can abstract from one or more of the aspects of a phenomenon without denying that these aspects are actually presented.

It has long been an object with philosophers to reduce the various mental faculties distinguished by language--sensation, feeling, reason, understanding, desire, imagination, memory, etc.--to certain more general forms. As early as Plato's Timaeus we find an indication of a tripartite division of the mind, in accordance with the later discrimination of the three faculties of knowledge, feeling and desire. Parallel with this threefold division runs another, into the higher and lower faculties. The former, the immortal reason, corresponds to knowledge; the latter, sensibility or the perishable part of mind, embraces feeling and desire. Feeling or emotion is here looked upon as mediating between reason and appetite, just as the true idea mediates between sensuous appearance and knowledge. But while sensation is expressly referred to the same part of the mind as desire,[24] the mediating thought (dianoia) and the emotion [p. 22] appear to stand in similar relation only to the faculty of reason. Hence these attempts at classification give us the impression two principles of division independently of each other,--the one based upon observation of a fundamental difference between the phenomena of cognition, feeling and appetition, and the other upon the recognition or stages in the process of knowledge; and that his not altogether successful attempt to reduce the two to one came only as an afterthought. In Aristotle the mind, regarded as the principle of life, divides into nutrition, sensation, and faculty of thought, corresponding to the inner most important stages in the succession of vital phenomena. It is true that he occasionally introduces other mental faculties in the course of his discussion; but it is quite clear that he considers these three phenomena as the most general. Desire, in particular, is subordinated to sensation.[25]

PLATO obtains his tripartite division by ranking the properties of mind in the order of ethical value; Aristotle obtains his, conformably with his definition of mind, from the three principal classes of living beings. The plant mind is nutritive only; the animal mind is nutritive and sensitive; the human mind is nutritive, sensitive and rational. We can hardly doubt that the classification, with its three separable faculties, was originally suggested by the observation of the three kinds of living things in nature. But, however different the source from which it springs, we have only to omit the distinction of nutrition as a specific mental faculty, and we find it coinciding outright with the Platonic division into sensibility and reason. Hence it cannot itself, any more than the various later attempts at classification, be regarded as a really new system.

The most influential psychological systematist of modern times, WOLFF, employs both of the Platonic divisions, side by side, but makes the faculty of feeling subordinate to that of desire. The consequent dichotomy runs through his whole system. He first of all separates cognition and desire, and then subdivides each of these into a lower and a higher part. The further progress is shown in the following table.

This classification has its proximate source in the Leibnizian distinction of ideation and appetition as the fundamental forces of the monads. It shows a great advance upon previous systems in not confining the faculty of feeling and desire to emotion and sensuous desire, but giving it the same range as the faculty of knowledge, so that the old difference in ethical value disappears. On the other hand, it is obvious that the special faculties grouped under the four main rubrics are not distinguished upon any systematic principle; their arrangement is purely empirical. The classification underwent many changes at the hands of WOLFF'S disciples. We frequently find knowledge and feeling taken as the [p. 23] two principle faculties, or feeling added as intermediary to knowledge and desire. This last scheme is that adopted by KANT. WOLFF'S thought, even in the empirical psychology, is guided by his endeavour to reduce all the various faculties to a single fundamental force, the faculty of ideation; and his rational psychology is largely devoted to this task. KANT disapproved of any such attempt to obliterate given differences in the mere effort after unification. Nevertheless, he too allows knowledge to encroach upon the domains of the other two mental forces, in correlating each of them with a special faculty within the sphere of cognition. But he maintains the original diversity of cognition, feeling and desire. The faculty of knowledge comprehends the other two only in the sense that it is the legislative faculty of mind at large. It is the source both of the concepts of nature and of the concept of freedom which contains the ground of the practical precepts of the will. It also produces the intermediate teleological judgments and judgments of taste. So we find KANT saying that understanding, in the narrower sense, legislates for the faculty of knowledge, reason for the faculty of desire, and judgment for feeling;[26] while understanding, judgment and reason are elsewhere bracketed together as understanding in the wider sense.[27] On the other side, KANT accepts the distinction of a lower and a higher faculty of knowledge,--the former embracing sensibility and the latter understanding,--but rejects the hypothesis that they are separated by a mere difference of degree. Sensibility is, for him, the receptive, understanding the active side of knowledge.[28] Hence in his great Critique he opposes sensibility to understanding. When connected with sensibility, understanding mediates empirical concepts; alone, it gives us pure notions.[29]

It is evident that there are three principal points to be emphasised in the course of this whole development. The first is the distinction of the three mental faculties; the second, the tripartite division of the higher faculty of knowledge; and the third, the relation of this to the three principal faculties. Th first is, in all essentials, a legacy from the Wolffian psychology: the other two are peculiar to KANT. Previous philosophy had, in general, defended reason (logoV) as that activity of mind which by inference (ratiocinatio) gives account of the grounds of things. The definition was, however, compatible with various views of the position of reason. Sometimes, just as in Neoplatonism, reason was subordinated to understanding (nouV, intellectus); the latter is a source of immediate knowledge, while the activity of inference implies commerce with the world of sense. Sometimes, it was ranked above understanding, as the means whereby we penetrate to the ultimate grounds of things. Sometimes, again it was considered as a special mode of manifestation of understanding. Illustrations of all three views may be found in the scholastic philosophy. The cause of this varying estimate of the place of reason is to be sought in the fact that the term ratio was used in two distinct senses. On the one hand, it meant the ground of a given consequence of individual truths, the 'reason for'; on the other, the capacity of ratiocinatio, of inferring individual truths from their grounds of 'reasoning'. First of all, ratio makes its appearance among the mental faculties, in this latter significance, as faculty of inference; later on, it appears [p. 24] also as a faculty of insight into the grounds of things. And wherever the emphasis fell upon this second meaning, reason shone forth as the very organ and instrument of religious and moral truths, or as a purely metaphysical faculty contradistingished from understanding, whose concepts could never pass the bounds of outer or inner sense-experience. A definition which includes both meanings of 'reason' makes it the faculty whereby we penetrate the interconnexion of universal truths.[30] Now KANT set out from the first of the three views above mentioned, the view which regards understanding as the faculty of concepts and reason as the faculty of inference. And he might well be encouraged to attempt, by the help of logic, to carry out to its conclusion the division of the higher faculty of knowledge which this view adumbrates, seeing that he had already achieved entire success in a similar undertaking, his deduction of the categories. He accordingly assumed that, since judgment stands midway between concept and inference (conclusion), the faculty of judgment stands midway between the faculties of understanding and reason. He had however, in his great Critique, sought to bring the two aspects of the concept of reason into a more vital relation by his doctrine of the unconditioned. In the conclusion, reason subsumes a judgment under its general rule. Now it must proceed, in the same way, to subordinate this rule to a higher condition; and so on, until in the last resort it arrives at the idea of an unconditioned. This idea, then, in its various forms as mind, world and God, remained the peculiar property of reason in the narrower sense; while all concepts and principles a priori, from which reason as faculty of inference derives individual judgments, became the exclusive property of understanding. So we find reason playing a curious double part in the Kantian philosophy. As faculty of inference, it is the handmaid of understanding, charged with the and principles which understanding propounds. As faculty of transcendent ideas, it ranks high above understanding. Understanding is directed merely upon the empirical interconnexion of phenomena. If it follow the idea of reason at all, it follows it only as a regulative principle, which prescribes the course that shall lead to a comprehension of phenomena into an absolute whole,--something of which understanding itself has no conception. It is, however, this regulative office of the ideas of reason that gives them their practical value. For the moral law, in KANT, is not constitutive, but regulative; it does not say how we really act, but how we ought to act. At the same time, by the imperative form in which it demands obedience, it proves the truth of the idea of unconditioned freedom of the will.[31] In fine, then, reason legislates for the faculty of desire, just as understanding legislates for the faculty of knowledge. For feeling, which stands midway between cognition and desire, there then remains only the faculty of judgment, which in like manner stands midway between the faculty of concepts and the faculty of inference.[32] The three fundamental faculties of mind are thus referred to the three modes of manifestation of the faculty of knowledge distinguished by formal logic. And we see at once how largely this reference is the product of an artificial schematisation suggested by the logical forms. This intellectualism has also had its reactive influence upon the treatment of the mental faculties; KANT pays attention only to the higher expressions of his three principal faculties. Now it may [p. 25] be doubted whether the totality of phenomena embraced by the first faculty can properly be summed up in the word 'knowledge.' But, at all events, it is obvious that the limitation of pleasant and unpleasant feeling to the judgment of aesthetic taste, and the reference of the faculty of desire to the ideal of the good, are not suited to serve as the starting-point of a psychological consideration.

HERBART'S criticism of the faculty-theory is principally directed against the form which it had assumed in the systems of WOLFF and KANT. The heart of his argumentation lies in the two following objections. (1) The mental faculties are mere possibilities, which add nothing to the facts of the inner experience. Only the individual facts of this experience, the individual idea and feeling and what not, can really be predicated of the mind. There is no sensibility before sensation, no memory before the stock of ideas which it lays up. Hence these concepts, notions of possibility, cannot be employed for the derivation of the facts.[33] (2) The mental faculties are class-concepts, obtained by a provisional abstraction from the inner experience, and then raised to the rank of fundamental forces of the mind and used for the explanation of our internal processes.[34] Both objections seem to shoot beyond the mark at which they are primarily aimed; they tell against methods of scientific explanation which have found application in practically all the natural sciences. The forces of physics, e.g., do not exist apart, by themselves, but only in the phenomena which we term their effects; and the functional capacities of physiology--nutrition, contractility, irritability, etc. --are one and all 'empty possibilities.' Again, gravity, heat, assimilation, reproduction, etc., are class-concepts, abstracted from a certain number of similar phenomena, which have been transformed on just the same analogy as the class-concepts of the inner experience into forces or faculties, to be employed for the explanation of the phenomena themselves. Indeed, if we term sensation, thought, etc., 'manifestations' of mind, the proposition that the mind possesses the 'faculties' of sensing, thinking, etc., seems to give direct expression to a conceptual construction which comes naturally to us wherever an object evinces effects that must be ascribed to causes lying within and not outside of the object. Nor has HERBART any objection to raise against the use of the concept of force at large. But he makes a distinction between force and faculty. We assume the action of a force, in all cases where We have learned to look upon a result as inevitable under given conditions. We speak of a faculty, when the result may just as well not occur as occur.[35]

Objection has been taken to this distinction, on the ground that it presupposes a concept of faculty which is found only in the most unscientific form of the psychological faculty-theory.[36] Nevertheless, it must be conceded that the discrimination of the terms is not without significance. With the development of modern natural science, the concept of force has gradually assumed the character of a concept of relation. The conditions which it implies are always reciprocally determinant; it is on their co-operation that the manifestation of force depends; and the removal of either side of the conditions renders it null and void. Thus the concept of force is correctly used when, e.g., the tendency to movement, that has its source in the interrelations of physical bodies, is derived from a force of gravitation, whereby these bodies determine each the [p. 26] other's position in space. On the other hand, it is an over-hasty generalisation to refer the phenomena of falling bodies to a force of falling natively inherent in every physical body. If we thus translate the conditions of a certain set of phenomena, resident in a given object, into a force of which the object is possessed, and ignore the external conditions of the observation, we evidently have no criterion for deciding whether a variation in the effects of this object depends upon a variation in intrinsic or in extrinsic conditions. The result is confusion: disparate phenomena are brought together, and (what is of more frequent occurrence) related phenomena rested apart. Many of the forces distinguished by the older physiology--the forces of procreation, of growth, of regeneration, etc.--are, beyond all question, nothing more than manifestations of a single force operating under different circumstances. And the same thing is pretty generally admitted of the final ramifications of the doctrine of mental faculties,--of the distinction, e.g., between space-memory number-memory, word-memory, etc. Similarly, the older physics explained the phenomena of gravitation by appeal to a number of forces: fall by the force of falling, the barometric vacuum by the 'horror vacui,' the motions of the planets by invisible arms from the sun or by vortices. But, further, the habit of abstraction from the external conditions of phenomena may easily lead to the erroneous conception of faculty, of a force that awaits an opportunity to produce its effect: force becomes incarnate in a mythological being. It would, therefore, be unjust to psychology, were we to accuse her and her alone of this aberration. Only, she has the one great advantage over the sciences of inorganic nature, that their work has paved the way for her advance. In their hands, the general concepts that belong at once to the outer and the inner experience have been purged of the errors natural to the earlier stages of the development of thought. And along with this advantage goes the obligation to make us of it to the full.

HERBART not only realised the untenability of the faculty-theory; he arrived at the positive conviction that mental processes must be considered as unitary processes. But he sought to satisfy the requirement of unity by raising one of the products of current psychological abstraction above all the rest. He regarded the idea as the real and only contents of the mind. Nay, he went so far as to declare that the idea, when once it has arisen, is imperishable, while all the other elements of mind--feelings, emotions, impulses--are merely the resultants of the momentary interactions of ideas. These opinions, as we shall see later, rest upon no better foundation than hypothesis, and bring their author, at every point, into conflict with an exact analysis of experience.[37] For the rest, it is obvious that the reduction of all mental processes to processes of ideation is a survival from the intellectualism of previous psychological systems. Nevertheless, HERBART had taken the right path in his endeavor to avoid that atomic conception of mental processes which simply repeats the mistakes of the old faculty-theory in less glaring form. Unfortunately. in escaping the one error, he was fated to fall into another. The fault of the older view is, not that it confuses unreality with reality, but that it substitutes for reality the products of our own discriminative abstraction.[38]

Footnotes

[1] The word was coined by Fechner; see his Elements der Psychophysik, 1860, i. 8. In this passage, Fechner defines psychophysics as an "exact science of the functional relations or relations of dependency between body and mind, or, in more general terms, between the bodily and mental the physical and psychical worlds"; and his main object in the Elemente is, accordingly, to establish the laws that govern the interaction of mental and bodily phenomena. It is clear that we have implied here the metaphysical assumption of a substantial difference between body and mind; we can hardly conceive, in any other way, of the existence of such a borderland, with facts and laws of its own. Fechner himself, however, rejected this substantial difference, for theoretical reasons: so that in strictness he could hardly have raised objection to such a purely empirical formulation of the problem of psychophysics as is given in the text. Cf. the concluding Chapter of this work.

[5] FECHNER, El. d. Psychophysik, ii. 9ff. An interesting light is thrown upon origination of the idea of 'mental measurement' in Fechner's mind, and also upon the inspiration that he derived from Herbart, by the "Kurze Darstellung eines neuen Princips mathematischer Psychologie" in his Zendavesta, 1851, ii. 373 ff. For a detailed treatment of mental measurement, see Ch. ix. below.

[10] MUNSTERBERG. Grundzüge der Psychologie, Vorwort, viii. C. the same author's Psychology and Life, 1899. This view, of the irrelevancy of psychology to the mental sciences, is further shared by certain modern philosophers: see the criticism of it in my Einleitung in die Philosophie, 1901, &sect; 4.

[12] On the doctrine of association. see Part v., below. For a general criticism of psychological materialism, cf. the articles Ueber psychische Causalität and Ueber die Definition der Psychologie, in the Philos. Studien, x. 47 ff., xii. 1 ff.

[15] In my Grundriss der Psychologie (4te Aufl. 1901; Outlines of Psychology, 1897), in which I have attempted to give an elementary exposition of psychology so far as possible under the exclusive guidance of psychological principles, I have adhered more strictly to the systematic point of view. Hence the Grundriss may be regarded in this connexion both as a supplement and as introduction to the present work.

[16] For a more extended discussion of these terminological questions see Ch. vii. &sect; I, below.

[17] Gemüthsbewegungen, as first used above, means "complex affective, affective-volitional and volitional processes." There is no exact English equivalent. See BALDWIN'S Dict. of Phil. and Psych. ii. 1902, 680. Willenshandlungen means, of course, voluntary actions, internal and external.--TRANSLATOR.

[18] In the first four editions of the Physiologische Psychologie, the Introduction consists of two sections, entitled respectively Aufgabe der physiologischen Psychologie, and Psychologische Vorbegriffe. In the present, fifth edition, the second of these sections is replaced by an Uebersicht des Gegenstandes. I here reprint the section on Psychologische Vorbegriffe as it appeared in 1893. It was, in all probability, omitted mainly for reasons of space. Cf. Preface to this fifth edition. It will, I think, be found useful by English readers in its present form, although a good deal of its criticism is implicit in the constructions of the final chapter of the work. I print it only after much hesitation, and with the express reminder to the reader that the author, for whatever reason, has not included it in the current edition of his book.--TRANSLATOR.

[19] The German terms for 'body' and 'matter' are Leib and Körper; for 'mind' and 'spirit,' Seele and Geist. See BALDWIN'S Dict. Of Phil. and Psych., ii. 680.--TRANSLATOR.

[20] Timaeus, 35. JOWETT'S Plato, iii. 453-4.

[21] The Aristotelian definition of mind in general as 'earlier or implicit entelechy (i.e. perfect realisation) of a natural body possessed potentially of life,' holds also of the (logoV nouVpoihtikoV), the spirit as independent of sensibility. Spirit is, however, the reality of the mind itself, and so can be conceived of as separated from the body; which is not the case with the other parts of mind. De anima, ii. sub fin. WALLACE's trans,. 65; HAMMOND's trans. 44 f.